The correct option is C Crossing of two inbred parental lines
Hybridization or crossing of two unrelated individuals or parental lines leads to hybrid vigor or heterosis. So in maize, hybrid vigor can be exploited by the crossing of two inbred parental lines. Since the parents are inbred the parents will have superior characters and when they are crossed the offspring will have the superior characters of both the parents.
Induced mutations have been used to improve major crops such as wheat, rice, barley, cotton, peanuts, and beans, which are seed propagated.
Bombarding of seeds with DNA is a process of genetic engineering
Harvesting seeds from the most productive plants are a part of germplasm collection the first step in plant breeding.